There are various processes for refining a variety of residues by hydrogenation in refinery. For example, the processes include desulfurization or denitrification of naphtha, kerosene, or diesel oil; desulfurization or denitrification of heavy diesel oil; desulfurization or denitrification of residual or heavy oil.
Among these processes, a catalyst used in hydrogenation for naphtha, kerosene or diesel oil, which has a relatively low boiling point and contains almost no metal impurities such as vanadium deteriorates less according to the use of the catalyst. In addition, the deterioration of such a catalyst is caused by accumulation of a very small amount of carbonaceous materials, and this catalyst can be reused by only combustion. In addition, in the aspect of the removal of the carbonaceous material, a reusable catalyst can be easily obtained without precise combustion control because a small amount of carbonaceous materials is included in the catalyst. In addition, a catalyst that deteriorates less even when it is used can be reused without any treatment. Such a catalyst is used again in treatment of naphtha, kerosene, diesel oil, etc. without special care.
In addition, a hydrogenation catalyst for heavy diesel oil or vacuum diesel oil is recycled by regeneration, and methods of regenerating and using the same are established. For example, it is known that a hydrocracking catalyst used in a heavy diesel oil hydrocracking process, or a hydrodenitrification catalyst for pretreatment is regenerated by hydrogen activation or oxygen activation. Since above-mentioned oils have almost no metal impurities, metal foulants such as vanadium are also less deposited in the catalyst. In addition, carbonaceous materials deposited on such a catalyst are also easily combustible, and thus a surface of the catalyst was not heated enough even when regenerated by combustion. Moreover, a micropore structure of a catalyst supporter or an impregnated state of an active metal was less changed, and the catalyst had been used in treatment of split oil such as heavy diesel oil or vacuum diesel oil (refer to Studies in Surface and Catalysis vol. 88 P199 (1994)).
However, in hydrogenation of heavy oil or residual oil including residues, which has a higher boiling point or is not easily distilled, the crude oil includes a large content of metal impurities, and a large content of easily carbonized components such as an asphalt component. Accordingly, the metal impurities or carbonaceous materials was simultaneously deposited at a large content on the completely used catalyst, and thus these materials could not be simply removed by combustion (refer to Catal. Today vol. 17 No. 4 P539 (1993), Catal. Rev. Sci. Eng. 33 (3 & 4) P281 (1991)). For this reason, the used catalyst was not recycled and was disposed of.
An amount of heavy oil hydrogenation catalyst, particularly, a heavy oil residue hydrodesulfurization catalyst, consumed worldwide is rapidly increasing due to the building and upgrading of highly developed facilities (heavy oil cracking process), which is now known as a second oil field among the developed countries as well as in Korea, and the four refineries in Korea are now showing 23,000 tons per year. These catalysts are dependent on imports, import prices are currently approximately $20/kg, and approximately 500 billion KRW a year or more relies on such imports.
The heavy oil residue hydrodesulfurization catalyst has a life span of 3 to 4 months as a guard catalyst (from which metals are mostly removed in a heavy oil desulfurization unit), and approximately 1 year as a main catalyst. After use, the catalyst is crushed to recover only valuable metals, or buried as a waste material if it is less economical.
In general, as a representative method of recovering valuable metals from a spent catalyst for petroleum desulfurization, a high temperature soda method, a solvent extraction method, an ion exchange method, or a precipitation method is used. Depending on a metal to be recovered, valuable metals are recovered in an oxide type through water leaching after low temperature roasting or high temperature roasting, selective precipitation, and calcination. On the other hand, in Korea Patent Publication No. 2001-0022250, a method of regenerating heavy oil hydrogenation including cleaning a spent catalyst using a solvent, and removing a carbonaceous material by combustion under an oxygen atmosphere is disclosed. However, even according to this method, vanadium present in the spent catalyst could not be selectively removed.